How can i find out who deleted files?

Hi Nicola, 

Welcome to the Box Community!

If you have Admin privileges with permission to run "reports", generating a User Activity report would be helpful as it provides an overview of the actions your users are taking in Box.

Use this report to view all the actions made by your users (from moving, deleting, renaming folders, etc) within a given time period and then you can filter by action type using the dropdown below the header. To run this report:

• Go to the Admin console > Reports
• Under Reports> Click User Activity
• You can choose to create a report for a specific managed user or group or leave the Users or Groups(optional) field blank for a company wide report (this means the report will reflect all your users actions)
• Then enter given time period of the report you want to created (fill in the Start Date and End date of when you noticed changes were made)
• Then, filter by Action Type using the dropdown below the header. In your case, you will want to choose File Management, and then select the specific action/s of your users you want to review, you'd want to choose "Moved to Trash" for this incident.
• You can choose to Run or Export the file to your Box Report folder and it should appear once its ready.

You can review the users' activities to see who have been deleting the files in your organization.

Check out Running Reports to learn more about reports in Box.